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UCC28180: input capacitor

K.Yaita
Guru 29720 points
Part Number: UCC28180

Hi Team,

1)
The following calcuration of input capacitor shows "recommended value" and I believe it isn't refered to "mimimum value".
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Is there maximum value of input capacitor for operating normal operation of PFC?


2)
The calcuration above include VIN_RECTIFIED(min).
Why does it adopt VIN_RECTIFIED(min) not VIN_RECTIFIED(max)?


Best Regards,
Yaita / Japan disty

  • 0
    TI__Expert 3095 points

    Hi K.Yaita,

    The capacitor calculated is the value required to meet the specified target of 7% at peak of low line.

    The highest ripple current occurs at peak of low line, hence the ripple voltage calculation is done for this condition.

    Thanks

    Joe Leisten

  • 0 in reply to Joe Leisten
    Guru 29720 points

    Hi Joe-san,

    Thank you for your kind support.

    Is there maximum value of input capacitor for operating normal operation of PFC?
    (Is there any concern if input capacitor is significantly larger than calculated value?)

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Expert 3095 points
    Hi Yaita-san,
    No problem if a larger capacitor is used.
    Increasing the input capacitor will slightly degrade pf and THD. This is a small effect and even if you double or triple the calculated value the effect will be small.
    Thanks
    Joe Leisten